Quiz - Equipment - J-Valve

[scubadada]

Can't be done, not if the Jvalve is working properly.

You have breathed down a cylinder with a J valve to essentially empty without opening the valve? What was the breathing resistance like, constant, or did increase?

 

[Scuba Lawyer]

You have breathed down a cylinder with a J valve to essentially empty without opening the valve? What was the breathing resistance like, constant, or did increase?

Interesting. I have not done as you suggest; however, logically it would seem that the lower the tank presure, the less force available to hold the spring back and the breathing resistance would increase until the tank pressure was insufficient to hold the spring back at all (thereby shutting off supply of air until the valve is activated). Seems right but happy to be proved wrong.

 

[wetb4igetinthewater]

Linear, not exponential.

The equation is: F = kx

Force = spring_constant * displacement

Hooke’s Law. Just looked it up.

 

[agilis]

You have breathed down a cylinder with a J valve to essentially empty without opening the valve? What was the breathing resistance like, constant, or did increase?

No, I've never breathed a cylinder to anything near empty. I apologize if i was unclear. My experience with J valves was unremarkable. A J valve is like any other valve when the lever is down/disengaged. When it's engaged you will experience some breathing resistance rather quickly as you approach the PSI spring pressure setting. It was not particularly gradual. As resistance is perceived, you just pull the actuating rod removing the spring pressure. As I recall, breathing effort then became about the same as it was at the start of the dive. It all happened pretty quickly, with breathing easy and fine until suddenly it wasn't.

 

[tursiops]

No, I've never breathed a cylinder to anything near empty. I apologize if i was unclear. My experience with J valves was unremarkable. A J valve is like any other valve when the lever is down/disengaged. When it's engaged you will experience some breathing resistance rather quickly as you approach the PSI spring pressure setting. It was not particularly gradual. As resistance is perceived, you just pull the actuating rod removing the spring pressure. As I recall, breathing effort then became about the same as it was at the start of the dive. It all happened pretty quickly, with breathing easy and fine until suddenly it wasn't.

Concur.

 

[TMHeimer]

Whoa, did I just read the official answer is A and 72.1% got it WRONG? That's a lot of people who are very experienced and possibly pro. Maybe something IS wrong with the wording???

 

[Scared Silly]

The J and K valves are named after the letter in the catalog. So where did the P-valve get its name?

 

[dead dog]

Of course it was a 1/4" suit. But now I use the metric system if possible.

Why?

 

[tursiops]

Why?

It makes sense, it communicates better in most of the world, it is easy to work with.
It is like speaking two languages....if you use them both, they are not hard to use. In some situations one will work better than the other.
My guess is if I'm speaking to you, I better use Imperial if I want to be understood. Right?
But if I've got an M8 bolt in my hand from my camera housing, and want another, I'm not gonna translate that to Imperial.

 

[tursiops]

Whoa, did I just read the official answer is A and 72.1% got it WRONG? That's a lot of people who are very experienced and possibly pro. Maybe something IS wrong with the wording???

Well, actually, no, 72.1% did not get it wrong....83.6& got it wrong. Answer (c) is not correct; it is not extra air like you would have in a pony; it is the same air you started with but couldn't get at because of the J-valve, unless you mistakenly dove with the lever down, in which case you could get at it but then (a) is wrong.....and it was never extra air anyway. It is like carrying an 8 cuft pony that you fill from your 80 cuft tank before the dive...so your main tank is now only 72 cuft.